Glass molding equipment in common use in the world for many years employ what is commonly called tong head assemblies which are pneumatically operated and which grasp the blown glassware, such as bottles, for movement from one place to another. A typical cross head assembly of the type being described is illustrated in FIG. 1 of the drawing.
The typical tong head assembly includes a cylinder body 10 to which a tong holder guide bracket 11 is mounted. The tong holder guide bracket 11 provides the support for a pair of scissors tong assemblies 12 carried upon a guide pin 13. In some applications, the tong holder guide bracket 11 will provide the support for three tong assemblies 12.
Each tong assembly 12 is actuated by a plunger 14 which is interconnected at its lower end to the scissors assembly and which extends upwardly above the tong holder guide bracket through a guide bushing 15. A compression spring 16 and retaining washer 17 maintain the plunger 14 extended and in place.
A cylinder 18 is positioned above the cylinder body 10. The cylinder 18 includes a piston 19 and its associated piston rod 20 extending through a guide aperture in the cylinder base 21.
The lower portion of the piston rod 20 is directly interconnected to the central portion of a cross head 22 positioned below the cylinder base 21. The cross head 22 includes arms 23 which extend outwardly to a position above each plunger 14. Adjusting screws 24 provide the necessary adjustment for accommodation and wear and varying lengths of the plungers 14.
The tong head assembly is supported in place within the molding equipment by means of an axle (not shown) which interconnects with the upper portion of the cylinder 18 centrally through a drive sprocket 25. The axle includes a central bore therein which is in pneumatic communication with the upper portion of the cylinder 18.
At predetermined times in the machine cycle, pneumatic pressure is applied to the top of the piston 19. As this occurs, the piston 19 is forced downwardly which, in turn, actuates the cross head and plungers 14 to close the tong assemblies 12. Release of the pneumatic pressure, under action of the springs 16, causes the pistion 19 to be returned and the tong assemblies 12 to be opened.
One of the inherent problems of tong head assemblies of this type arises out of the simultaneous actuation of both plungers and tong assemblies. Often a piece of glassware will not be engaged properly by one of the tong assemblies. When this occurs, the tongs associated with the tong assembly will not completely close thus preventing the plunger 14 from being completely depressed. The result of this is that the cross head cannot completely extend and consequently the other plunger and tong assembly will not operate fully.
The conventional tong head assemblies, as any piece of equipment, will eventually wear with repeated use. Wear is pronounced in the cylinder area and particularly in the piston rod guide aperture in the cylinder base 21. Additionally, the guide bushings 15 wear considerably under the repeated actuation of the plungers 14.
Whenever the wear in the cylinder and the various guide areas becomes too great, the assembly must be torn down and rebuilt. Often the expense of machining the guides and cylinder and providing the necessary repairs, exceeds the value of new replacement parts. Accordingly, it is often common practice to simply scrap the cylinder body with its integral cylinder base and the tong holder guide bracket.